Having an issue in an arrow defense game where my bullet collides with two enemy's who's hitboxes are overlapping on their leading side, causing both to be destroyed by a single bullet but only be counted as one.

Another way I find useful is to your bullets, add a variable called Target and as your turret fires you add the UID of the turret target to the bullets Target variable.

The reason for this is when the bullet hits the enemy you can use this to make sure that it will only hit that target. This also solves the problem that the turret is actually shooting at its target and not just towards it, as the bullet will collide with the first enemy it hits. But if you plan to make any form for "tactics" for your turrets you will have to add something like this, so the player can actually count on the turrets attacking the targets they should.